/*
 * CompositeList.java July 2006
 *
 * Copyright (C) 2006, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.core;

import java.util.Collection;

import wx.xml.simpleframework.xml.strategy.Type;
import wx.xml.simpleframework.xml.stream.InputNode;
import wx.xml.simpleframework.xml.stream.OutputNode;

/**
 * The <code>CompositeList</code> object is used to convert an element
 * list to a collection of element entries. This in effect performs a
 * root serialization and deserialization of entry elements for the
 * collection object. On serialization each objects type must be
 * checked against the XML annotation entry so that it is serialized
 * in a form that can be deserialized.
 * <pre>
 *
 *    &lt;list&gt;
 *       &lt;entry attribute="value"&gt;
 *          &lt;text&gt;example text value&lt;/text&gt;
 *       &lt;/entry&gt;
 *       &lt;entry attribute="demo"&gt;
 *          &lt;text&gt;some other example&lt;/text&gt;
 *       &lt;/entry&gt;
 *    &lt;/list&gt;
 *
 * </pre>
 * For the above XML element list the element <code>entry</code> is
 * contained within the list. Each entry element is thus deserialized
 * as a root element and then inserted into the list. This enables
 * lists to be composed from XML documents. For serialization the
 * reverse is done, each element taken from the collection is written
 * as a root element to the owning element to create the list.
 * Entry objects do not need to be of the same type.
 *
 * @author Niall Gallagher
 * @see wx.xml.simpleframework.xml.core.Traverser
 * @see wx.xml.simpleframework.xml.ElementList
 */
class CompositeList implements Converter {

    /**
     * This factory is used to create a suitable collection list.
     */
    private final CollectionFactory factory;

    /**
     * This performs the traversal used for object serialization.
     */
    private final Traverser root;

    /**
     * This represents the name of the entry elements to write.
     */
    private final String name;

    /**
     * This is the entry type for elements within the list.
     */
    private final Type entry;

    /**
     * This is the field or method that has been annotated.
     */
    private final Type type;

    /**
     * Constructor for the <code>CompositeList</code> object. This is
     * given the list type and entry type to be used. The list type is
     * the <code>Collection</code> implementation that deserialized
     * entry objects are inserted into.
     *
     * @param context this is the context object used for serialization
     * @param type    this is the collection type for the list used
     * @param entry   the entry type to be stored within the list
     */
    public CompositeList(Context context, Type type, Type entry, String name) {
        this.factory = new CollectionFactory(context, type);
        this.root = new Traverser(context);
        this.entry = entry;
        this.type = type;
        this.name = name;
    }

    /**
     * This <code>read</code> method will read the XML element list from
     * the provided node and deserialize its children as entry types.
     * This will each entry type is deserialized as a root type, that
     * is, its <code>Root</code> annotation must be present and the
     * name of the entry element must match that root element name.
     *
     * @param node this is the XML element that is to be deserialized
     * @return this returns the item to attach to the object contact
     */
    public Object read(InputNode node) throws Exception {
        Instance type = factory.getInstance(node);
        Object   list = type.getInstance();

        if (!type.isReference()) {
            return populate(node, list);
        }
        return list;
    }

    /**
     * This <code>read</code> method will read the XML element map from
     * the provided node and deserialize its children as entry types.
     * Each entry type must contain a key and value so that the entry
     * can be inserted in to the map as a pair. If either the key or
     * value is composite it is read as a root object, which means its
     * <code>Root</code> annotation must be present and the name of the
     * object element must match that root element name.
     *
     * @param node   this is the XML element that is to be deserialized
     * @param result this is the map object that is to be populated
     * @return this returns the item to attach to the object contact
     */
    public Object read(InputNode node, Object result) throws Exception {
        Instance type = factory.getInstance(node);

        if (type.isReference()) {
            return type.getInstance();
        }
        type.setInstance(result);

        if (result != null) {
            return populate(node, result);
        }
        return result;
    }

    /**
     * This <code>populate</code> method wll read the XML element list
     * from the provided node and deserialize its children as entry types.
     * This will each entry type is deserialized as a root type, that
     * is, its <code>Root</code> annotation must be present and the
     * name of the entry element must match that root element name.
     *
     * @param node   this is the XML element that is to be deserialized
     * @param result this is the collection that is to be populated
     * @return this returns the item to attach to the object contact
     */
    private Object populate(InputNode node, Object result) throws Exception {
        Collection list = (Collection) result;

        while (true) {
            InputNode next   = node.getNext();
            Class     expect = entry.getType();

            if (next == null) {
                return list;
            }
            list.add(root.read(next, expect));
        }
    }

    /**
     * This <code>validate</code> method will validate the XML element
     * list from the provided node and deserialize its children as entry
     * types. This takes each entry type and validates it as a root type,
     * that is, its <code>Root</code> annotation must be present and the
     * name of the entry element must match that root element name.
     *
     * @param node this is the XML element that is to be validated
     * @return true if the element matches the XML schema class given
     */
    public boolean validate(InputNode node) throws Exception {
        Instance value = factory.getInstance(node);

        if (!value.isReference()) {
            Object result = value.setInstance(null);
            Class  type   = value.getType();

            return validate(node, type);
        }
        return true;
    }

    /**
     * This <code>validate</code> method will validate the XML element
     * list from the provided node and deserialize its children as entry
     * types. This takes each entry type and validates it as a root type,
     * that is, its <code>Root</code> annotation must be present and the
     * name of the entry element must match that root element name.
     *
     * @param node this is the XML element that is to be validated
     * @param type this is the type to validate against the input node
     * @return true if the element matches the XML schema class given
     */
    private boolean validate(InputNode node, Class type) throws Exception {
        while (true) {
            InputNode next   = node.getNext();
            Class     expect = entry.getType();

            if (next == null) {
                return true;
            }
            root.validate(next, expect);
        }
    }

    /**
     * This <code>write</code> method will write the specified object
     * to the given XML element as as list entries. Each entry within
     * the given collection must be assignable from the annotated
     * type specified within the <code>ElementList</code> annotation.
     * Each entry is serialized as a root element, that is, its
     * <code>Root</code> annotation is used to extract the name.
     *
     * @param source this is the source collection to be serialized
     * @param node   this is the XML element container to be populated
     */
    public void write(OutputNode node, Object source) throws Exception {
        Collection list = (Collection) source;

        for (Object item : list) {
            if (item != null) {
                Class expect = entry.getType();
                Class actual = item.getClass();

                if (!expect.isAssignableFrom(actual)) {
                    throw new PersistenceException(node, "Entry %s does not match %s for %s", actual, entry, type);
                }
                root.write(node, item, expect, name);
            }
        }
    }
}
